Harry Watts was born in Buckingham, England, on 20 September 1888. It is unclear when he immigrated to Canada.

A labourer, Watts enlisted in the 37th Battalion in Toronto, Ontario, on 15 July 1915. After initial training in Canada, he and his unit left for England on SS Lapland on 27 November 1915. The battalion landed in Plymouth on 4 December 1915. Upon arrival in England, it provided reinforcements to Canadian units already in the field. Watts was transferred to the 12th Reserve Battalion before being posted to the 60th and then the 87th battalions.

On 4 April 1920, Watts died from chronic endocarditis (inflammation of the lining of the chambers and valves of the heart) in St. Michael’s Hospital, in Toronto. His death was attributed to his war service.